Vitamin E appears to protect the rat and mouse NO2 and O3. Exposure to these oxidant gases probably results in the oxidation of lung polyunsaturated fatty acids, in the same manner as found in thin films or emulsions of PUFA. Phenolic antioxidants such as vitamin E retard this reaction in vitro. The more unsaturated the PUFA the more readily it is oxidized. Can dietary alterations of the lung PUFA or lipid antioxidants (vitamin E or synthetic phenolic antioxidants) ameliorate or enhance the deliterious effects of oxidant gases? Bases on experiments with rats, a second species, mice, will be fed chemically defined diets that either increase or decrease the ease of oxidation of lung lipids. Vitamin E will be absent, present at vitamin levels or pharmacological levels. The survival, morphological and biochemical alterations of lung on oxidant exposure will be determined to establish if oxidant gases degrade the lung by oxidation and, if so, what chemical species are promoting the reaction. Animals must be free of respiratory infections to provide reproducible responses. Accordingly, specific pathogen free mice will be used and exposed in chambers supplied at all times with bacterial and dust free air.